A first category of writing instruments of this type relates to devices in which the eraser holder is mobile in translation and prevented from rotating with respect to the shaft, and the protection sleeve is mobile in rotation with respect to the shaft while prevented from translational motion except optionally for the actuation of a feed mechanism of a writing cartridge. Means for preventing the rotation of the eraser holder with respect to the shaft conventionally comprise at least one first longitudinal guiding member such as a groove or a rib provided on the holder and interacting directly with a first complementary longitudinal guiding member provided on a part prevented from rotation with respect to the shaft. The means allowing for a relative translational motion between the eraser holder and the sleeve conventionally comprise at least one second guiding member such as a spiral groove or a lug provided on the holder and interacting with a second complementary guiding member connected to the sleeve.
An example of a writing instrument in this first category is described in U.S. Pat. No. 5,683,191, which relates to a propelling pencil, the lead feed of which is actuated by the user pressing on the protection sleeve in order to displace the latter in translation with the lead container tube. In a first embodiment, the eraser holder has at the front a tubular projection with a polygonal cross-section slidably fitted in contact around a rear portion of the lead container tube that has a cross-section with a complementary shape. The displacement in translation of the eraser holder is thus guided while prevented from rotating with respect to the lead container tube. The eraser holder is surrounded over its whole length by the protection sleeve which comprises a tubular projection capable of sliding against the inner wall of the shaft. This device however has certain drawbacks, in particular owing to the fact that two tubular elements are arranged radially between the lead container tube and the shaft, leaving a restricted central diametral space and disadvantaging the capacity of the lead container. Moreover, radial clearances are required between the tubular elements inside the shaft so that the latter can slide against each other, and the multiplicity of these clearances compromises keeping the eraser holder in axial alignment with the shaft.
A second category of writing instruments of this type relates to devices in which the eraser holder is prevented from translation with respect to the shaft, except optionally for the actuation of a feed mechanism of a writing cartridge, and the protection sleeve is mobile at least in translation with respect to the shaft. For a device of the propelling pencil type, the eraser holder is generally firmly connected to the rear end of a lead container tube that can be displaced in translation in the shaft in order to feed the lead only. The eraser holder therefore remains immobile in the shaft when the protection sleeve is displaced between the retraction configuration and the maximum exit configuration of the eraser.
An example of a writing instrument in this second category is described by the registered Japanese utility model JP2558803Y2, which relates to a propelling pencil, the lead feed of which is actuated by the user pressing on the protection sleeve in order to displace the latter in translation with the lead container tube. The sleeve has a front portion surrounding the rear end of the shaft. The eraser holder is firmly connected to the rear portion of the container tube by an intermediate tube comprising protrusions interacting with locking means provided on the sleeve in order to immobilize the sleeve in one or other of the retraction or maximum exit configurations of the eraser. However, this device has certain drawbacks, in particular owing to the fact that the locking means are relatively difficult to produce and furthermore there is a risk of the locking means becoming accidentally unlocked by the user while erasing. Moreover, the device does not include a system for locking the lead feed, as a consequence of which the use of the eraser while holding the writing instrument by the shaft risks causing a feed movement of the eraser holder towards the shaft and therefore the unwanted feeding of the lead.